For decades, epidemiologists have regarded income level as an important variable in their efforts to identify risk factors for cancer and many other chronic illnesses. According to a new report published this week the journal Cancer, household income levels are very important in predicting which type of cancer one may get and whether the cancer will be fatal.

A team of researchers located around the U.S. and lead by Francis Boscoe at the New York State Cancer Registry looked at almost three million incident cancer cases between 2005 and 2009 among 42 percent of the U.S. population, covering income levels from the very highest to the lowest. The cases were grouped by poverty rate assessed by residential census tract data during the study period.

They found that the risk of getting any cancer was not much different in impoverished versus wealthy neighborhoods. However, they found that for 32 of 39 cancer types considered, poverty was a significant variable. Higher poverty level was positively associated with 14 types of cancer, whereas higher wealth was positively associated with 18 cancer types.

Cancers linked to modifiable behavior risk factors such as tobacco, alcohol, and diet occurred more frequently in high poverty areas. Among these were human papilloma virus-associated cervical cancer, liver cancer, and lung and esophageal cancers. Higher income communities suffered more thyroid, skin, and prostate cancers.

The cancers that occur more frequently in the higher poverty regions were more deadly.  The researchers speculate that access to healthcare is probably a key determinant in lethality.

“Wealthier communities are more engaged with the health care system and have more frequent screenings,” said Boscoe. Poverty data are rarely recorded in public health data systems, according to Boscoe, who also emphasized that racial and ethnic groupings must be considered distinct from income level.

“Even when you stratify by race, such as in the case of prostate and lung cancers, you still see differences in incidence rates even within race. So you end up having very distinct relationships by race and socioeconomic status that are different from one another in certain types of cancers,” Boscoe said.